This invention relates to arrangements for initializing and updating the memory of mobile telecommunications stations.
In order to define the service that is provided to a mobile telecommunications station, usually a mobile telephone station, it is necessary to initialize, and subsequently update the data for defining the service capabilities that is stored in a non-volatile electrically alterable memory of the station. For example, the telephone number of the station is retained in its memory.
Also retained is information for defining the areas where roamer service is provided to the station. Roaming service is service provided by a service provider other than the primary service provider for providing service to the station when the station is not in its own local or home area. Complicated sets of agreements define which carrier, if any, will handle calls when the station is outside its own local area. Each station has a list of system identifiers of systems that will serve that station through roaming agreements. When a station turns on power, when it is outside its own local area, it scans for a sufficiently strong signal from a control channel. It identifies itself to that control channel along with a called telephone number, and the initial message from that control channel will contain the system identifier of that control channel. The system identifier contains information identifying a service provider, (carrier), and the area which the control channel serves. (Thus, for example, ATandT in Texas will have a different system identifier than ATandT in Illinois).
If the system identifier provided by the carrier is on a list of the system identifiers that serve the station, then further messages are exchanged over that control channel in order to register the mobile station. If the mobile station is not in its home area, then a Visitor Location Register, (VLR) entry is created for the registering station based on information received from the Home Location Register, (HLR) information for that station obtained via the IS-41 signaling network. (IS-41 is a signaling standard that overlays the Signaling System 7 signaling standard. IS-41 adds features that support mobile communication such as cellular telephones and Personal Communication Systems (PCS).)
If the system identifier provided over the control channel originally addressed is not on the list of system identifiers stored in the mobile station, then the mobile station will look for another control channel over which it can communicate with another service provider, and will make a similar attempt.
If all attempts to reach a service provider result only in finding service providers whose system identifier is not on the list stored in the mobile station, then normal registration cannot take place. In some cases, the mobile simply cannot make a call. In other cases, the mobile can reach an operator of a service provider and place a call, such as a calling card call, for which the service provider completing the call can be assured of receiving payment even if there is no agreement with the local service provider of the mobile station. Emergency calls, such as E-911 calls, are not blocked by roaming agreements, and will be completed by the carrier of the initial control channel over which the mobile station sends its request
The above description has served as an explanation for the requirement that the mobile station store a list of system identifiers for service providers with which the local service provider has made a roaming agreement. Mobile stations that comply with the IS-683A standard can store hundreds of such agreement entries. (IS-683A is a standard for Code Division Multiple Access (CDMA) digital radio used in cellular telephones. IS-683A is also used in CDMA Personal Communication Systems (PCS).)
It will be appreciated that the contents of that list should be altered whenever new agreements are made. If the new agreements add territory, failure to alter the list provides degraded service to the subscriber, since the subscriber will not be able to take advantage of the increased roaming area. If a change is made in the service provider for an area in which roaming was already possible, then the subscriber will be denied roaming service where the subscriber already had roaming service, and where roaming service would, in fact, would be possible through parameter changes that reflect the changed agreements. Accordingly, it is important that telephone stations be updated whenever the roaming list changes, a phenomenon which, at the present time, may happen as frequently as monthly. Other data which is stored in the memory of the mobile station may also have to be changed. For example, if the area code of a large number of mobile stations is changed, the revised area code must be provided to all affected mobile subscriber stations in a relatively short interval of time.
A problem of the prior art is that the arrangements for updating memory in, for example, an IS-683A mobile subscriber station, require a large number of airwave messages.
These messages are not carrying subscriber traffic, which would produce revenue for the service provider, and consequently, are seen as a cost to the service provider in a given cell. In the IS-683A airwave standard, a cell has a finite number of airwave codes to allocate to subscribers. If a mobile station is using one of these finite resources for receiving parameter update messages, another mobile station in that serving cell may be blocked from service, even if that service could otherwise produce revenue for the service provider. Even if there are sufficient resources to satisfy all subscribers, including those receiving parameter updates, it is also possible that the subscriber can de-register the mobile station, (e.g., powering-off the mobile station), before the parameter updates have completed. In such a case, the entire update sequence must be repeated from the start. In the prior art, where a large number of airwave messages are required to perform parameter update, (sometimes extending over four minutes), de-registration of a mobile station before successful update is a high probability. Another problem of the prior art is that the human interface between the system administrator and the computer system for generating these airwave messages is awkward, requiring extensive interaction between the system administrator and the computer system, and requiring of the system administrator an expert level of detailed knowledge of the internals of IS-683A mobile stations. Service providers are consequently burdened with the additional cost of training and maintaining a high skill level in these administrators.
Applicants have further analyzed the characteristics of the prior art arrangement. Mobile stations complying with the IS-683A airwave standard have parameters that are updated in blocks. For example, the already mentioned roaming list is one parameter block. Likewise, the directory number of the mobile station lies within a different parameter block. The prior art re-initializes all memory within a parameter block, even parameters that do not need to be updated. Thus, the prior art results in larger number of messages than are necessary to update changed parameters in an IS-683A mobile station. Moreover, the prior art requires a detailed knowledge of the memory layout of an IS-683A mobile station in order to create a parameter block that can properly overwrite the one existing in the mobile station. Finally, the prior art requires a detailed knowledge of the protocol procedures required to load the updated parameter block into the mobile station.
The above problems are substantially alleviated, and an advance is made over the teachings of the prior art in accordance with Applicants""invention, wherein an object model represents all of the parameters that can be modified in an IS-683A mobile station. The details of the physical location of each parameter, as well as the necessary protocol procedures, (implemented in the set of airwave messages), are defined within this mobile object model. Hence, when any parameter is added or changed, it is necessary to provide the computer system only the identification of the parameter to be added or changed, and the value of that parameter. The computer system can then prepare a message sequence that defines the memory location in the mobile station to be changed, and the new value of the data for that memory location. Advantageously, this arrangement sharply reduces the total number of airwave messages transmitted to the mobile station, thus reducing the amount of required air time for a change, and reducing the probability that a mobile station will de-register before the updating process is complete. Advantageously, this arrangement greatly simplifies the task of the system administrator in preparing such changes. Advantageously, because of the great simplification of the process, and the reduction of the number of airwave messages sent to the mobile station, it is possible to make more small changes in parameter blocks such as the roaming list, instead of requiring such changes be aggregated into an occasional much larger change.